chore: backporting changes to merge-forward job from v2 branch (#12482)

Bringing the two branches back into sync.

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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: njlynch

scripts/merge-forward.sh

@@ -6,8 +6,11 @@ set -exo pipefail
 git fetch --all
 git checkout -B v2-main origin/v2-main
 
+git merge origin/master --no-edit
+
 # Some package rules differ between v1 and v2, most notably which packages can be public vs private.
 # These differences are fixable via 'pkglint', so we run that and commit the delta (if any).
-lerna run pkglint && { git diff --quiet || git commit -am 'automatic pkglint fixes'; }
-
-git merge origin/master --no-edit
+yarn install --frozen-lockfile
+yarn pkglint
+# Commit the difference, if there is one.
+git diff --quiet || git commit -am 'automatic pkglint fixes'